In a facility such as a power generating plant in operation, where operating conditions are relatively harsh or safety must be ensured, it is necessary to monitor deterioration in strength of a constituent member used in the facility in operation. Further, it is necessary to predict a remaining service life of a constituent member and carry out maintenance service at a proper timing.
For this purpose, when it is intended to continue the operation of the facility, it is a common practice to employ a nondestructive testing method for inspecting the constituent member in the facility.
On the other hand, instead of the nondestructive testing, a material may be taken out as a test piece from the constituent member of the facility. In this case, a member may be replaced as a whole before taking a test piece therefrom, or a large member may be transported to a factory where a test piece can be taken from the member.
Accordingly, a test piece or other material piece is taken after transporting the member to be tested to a facility equipped with a sampling device, rather than transporting a sampling device to a field and taking a test piece from the constituent member of the facility in the field.
Also, in a case that a constituent member of the facility has a defective portion in a surface thereof, it is necessary to remove the defective portion from the member, so that the removed portion can be tested as required. However, it is difficult to provide a device which can be carried to the field and is capable of readily removing the defective portion from the constituent member of an operating facility.
The test piece or other material piece taken out of the constituent member of the facility is subjected to mechanical or other test. Accordingly, if the test piece is changed in nature thereof due to deformation during the extracting operation or the accompanying heat, it is difficult to accurately evaluate the sample. According, it is necessary to prevent the deformation of the constituent member of the facility during the extracting operation or the accompanying heat as much as possible.
To this end, for example, an electric discharge machine may be used to sample a test piece or remove a defective portion.
The electric discharge machine is a device for machining an object by generating an electric discharging between the device and the object. With the device, it is possible to reduce an area of the object subjected to machining strain within a relatively narrow region.    Patent Reference 1: Japanese Patent Publication No. 2001-79658    Patent Reference 2: Japanese Patent Publication No. 10-76427,    Patent Reference 3: Japanese Patent Publication No. 10-2988,    Patent Reference 4: Japanese Patent Publication No. 9-218139,    Patent Reference 5: Japanese Patent Publication No. 9-155646,    Patent Reference 6: Japanese Patent Publication No. 7-159295
In the nondestructive testing method described above, it is not possible to measure an actual mechanical strength. Accordingly, it is difficult to estimate deterioration of the constituent member of the operating facility and predict the life.
A conventional test piece sampling device is a fixed type of a heavy weight, and is suitable for such an application in which the test piece sampling device is transported to a sampling site and is set for an operation of sampling a constituent member of an operating facility.
When the electric discharge machine is used to sample a test piece or other material piece, it is possible to minimize undergoing mechanical and thermal deformation on the test piece thus obtained. However, the conventional electric discharge machine is a machining tool in nature, and a principal object thereof is not to obtain a material piece. Therefore, the electric discharge machine is not convenient for sampling a material piece.
When a conventional device disclosed in Patent References 1 to 6 is used to obtain a material piece, it is necessary to repeat an operation of moving an electric discharge electrode several times until the material piece is sampled, thereby causing problems related to an operating procedure and an operating time. In addition, the conventional device can rotate and move the electric discharge electrode simply along an arc-shaped trajectory. There has not been any device capable for conveniently and easily adjusting a trajectory of an electric discharge electrode.
Accordingly, an object of the present invention is to solve the problems described above and provide a material piece scooping device with a compact construction capable of sampling a test piece or removing a defective portion from a pipe and other constituent member of a facility at a site, while minimizing deformation caused by an extracting operation or accompanying heat.